I think some of the scoffers on MN confuse (deliberately) middle class for upper-middle class, and call lower-middle class working class.
I think, on here, most of the people being told they are working class are middle, or lower-middle.
Eg, people who have a good/above average-paying job, own a mortgaged home in a nice area, have a decent car (even if it's on <gasp> PCP), holiday in Spanish AI hotels that are 4-5 star, have children who do all the activities, buy clothes from the high street etc - these people are middle class. I think culture is now so wide among the middle class that people within it will frequently have interests and do activities on a spectrum of what would have been considered upper/middle/working class.
The people who have been given 500k to buy a house outright by their parents when they turned 18 and have horses and don't need to work due to family generational wealth and investments are not middle class, they're upper.
People on low wages/benefits, for whom life is a struggle and with little-to-no security in their finances, job, and housing are working class. Culture is limited, not because they are incapable of appreciating the opera/ballet/skiing/humanities degrees for the joy of learning, but because it's too expensive to be something they could realistically do (or do frequently) so they can't get into it.